In the field of electronics, printed circuit boards (PCBs) provide a compact structure for packaging electrical components and circuits. PCBs are commonly used in electronic assemblies, so it is typically the case that electrical signals are conveyed between the PCBs and other components of a larger assembly. To that end, multi-pin connectors provide one mechanism for establishing an electrical coupling to traces on the PCB for the purpose of transmitting signals to and from the PCB. Multi-pin connectors provide an advantage of packaging a relatively large number of signal conduits in a small volume. In other cases, it is also necessary to provide point connectivity to a relatively small number of traces on a PCB. For example, a single contact is sometimes used to connect a PCB to an antenna or to a reference voltage such as ground. In these cases, it is sometimes feasible or necessary to use a single contact that couples the PCB to a separate component in the electronic assembly.
A variety of solutions are known for providing point-contact connectivity to a PCB. Leaf springs and coil springs are examples of the types of contacts used for this purpose. In fact, leaf springs and coil springs are also used in multi-pin connectors, which may simply be thought of as a conglomeration of point-contact connections. These individual contacts are often spring biased to help establish sufficient contact force between conducting surfaces and improve electrical connectivity. Unfortunately, coil springs and leaf springs are not always preferable for certain applications. As an example, coil springs are generally characterized by high impedances at RF frequencies making them impractical for use with antennas.
Leaf springs offer a viable alternative to coil springs, particularly for use in conveying high frequency signals. Leaf-spring contacts are known in the art and are generally available off the shelf. However, certain disadvantages are present with existing solutions. For instance, many existing leaf spring contacts have a limited spring range, making them impractical for use where an electrical connection needs to be established between the PCB and a component that is positioned a relatively large distance away from the PCB. This situation would seem ideally suited for a coil spring were it not for the impedance limitations discussed above.
Furthermore, many leaf spring contacts have a large pick-up surface for lifting and placing the contact on a PCB or into an assembly. This pick-up surface is particularly required where a vacuum pick-up is used to place the contact during assembly. With conventional leaf spring contacts, the enlarged pick-up surface is placed at a distal end of the contact opposite the mounting surface (i.e., where the contact is mounted to the PCB or other component). Thus, the pick-up surface also functions as a connection surface once the contact is placed in the electronic assembly. Some disadvantages to this configuration include that the contact can be quite large and that the connecting surface is flat. A flat surface is not always optimal as a contact surface. In certain instances, it may be desirable to have a coined or shaped contact surface to control the characteristics of the electrical interface.
Another disadvantage of existing leaf spring contacts pertains to the elasticity of the contact. Spring biased contacts have a characteristic resiliency and the internal reaction forces caused by deflection of the contact help establish sufficient physical contact and electrical connectivity between electrical components. These reaction forces are an inherent property of the contact that are repeatable as long as the contact substantially retains its original shape. Certain factors that can adversely affect the shape of the contact include creep, fatigue, and plastic deformation. Creep and fatigue are often produced in high temperature, high stress environments and can generally be avoided by proper design and selection of the contact. Plastic deformation tends to change the shape of the contact and often occurs during assembly or use when the contact is deflected beyond the yield point of the base material. In layman's terms, the contact is bent so that it no longer makes sufficient, if any, contact between electrical components. In existing applications, a dedicated stop is generally required to limit deflection and prevent over-compression of a contact.